摘要:

The structure of the proventricular region of the bristle-tail,Machilis variabilisSay, is described. Its structure is found to be intermediate in complexity between that of the simple, tubular fore-gut of the Collembola and that of the muscular proventriculus of the silver-fish,Lepisma.

ISSN:1923-4287    

DOI:10.1139/cjr47d-011

出版商:NRC Research Press    

年代:1947

数据来源: NRC

摘要:

The wolf (Canis lupus occidentalis) population of the Rocky Mountain National Parks of Canada, an area of 7000 square miles of mountainous terrain, was studied from 1943 to 1946. During that time it approximated a density of one wolf to between 87 and 111 square miles of potential range, which was reduced to about 10 square miles per wolf during late winter by contraction of available range. The range is heavily populated with the wild ungulates,Ovis canadensis,Oreamnos americanus,Alces americana,Rangifer arcticus, andOdocoileus hemionus. Many of the winter ranges are grossly overstocked. The annual diet of wolves in the area has consisted of 80% big game, with elk alone contributing 47%. Mule deer contribute another 15%. Although bighorn sheep are in abundance and available they are little hunted by wolves. Eighteen per cent of the annual diet consists of rodents, of which snowshoe hare and beaver are the two most important. Wolves are unevenly distributed and many game herds have been living without wolf pressure. Comparison of the vital statistics of game herds living with and without wolf predation reveals no discernible difference in the survival of young or in the sex ratios within the two groups. It is concluded that under existing circumstances the wolves are not detrimental to the park game herds, that their influence is definitely secondary, in the survival of game, to the welfare factors, of which the absence of sufficient suitable winter forage is the most important.

ISSN:1923-4287    

DOI:10.1139/cjr47d-012

出版商:NRC Research Press    

年代:1947

数据来源: NRC